A power window regulator of an automobile is commonly equipped with a switch device which is designed with a knob provided on a casing in such a manner that a restoring force is applied to the knob at all times to return it to its original position. The knob is turned from the original position to a first operating position by pushing it. The knob is turned from the first operating position to a second operating position by pushing it again. That is, the knob is operated in two steps.
A motor operating switch is provided which is turned on when the know takes the first or second operating position, to complete the forward or reverse rotation circuit of the motor (or vice versa, depending upon the interconnetion between the switch and the motor), and to move the window in one or the other direction, depending again on the particular mechanical interconnection between the motor and window apparatus. In addition, a holding switch is provided which, when the knob is moved to the second operating position, is turned on to apply current to an electromagnetic solenoid adapted to attract and hold the knob at the second operating position. Therefore, when the knob is kept in the first operating position, the window is continuously moved.
When the knob is set at the second operating position, the window is moved until the window is fully opened or fully closed even if the knob is released. When the window has been fully opened or closed, the driving motor is stopped and locked. In order to overcome this difficulty, a detecting device has been employed to determine when the window has reached the fully open or fully closed position.
The detecting device normally includes a contactor to which direct current is applied and which is brought into contact with a sector wheel. The sector wheel is coupled to a lever to move the window directly and to engage a pinion driven by the motor. A detecting circuit detects spike-shaped noise induced in the contactor as the contact resistance changes with movement of the sector wheel. A transistor connected in series to the above-described electromagnetic solenoid is turned on as long as the detecting circuit detects the noise, so that when the detecting circuit detects no noise, i.e., when the motor is stopped in a locking manner with the window fully opened or closed, the transistor is turned off to stop current flow to the electromagnetic solenoid. The knob is then returned to its original position to deenergize the motor.
This construction is disadvantageous in that the detecting device is intricate and causes the power window regulator switch device to be large in size and high in manufacturing cost. Moreover, the switch device requires a relatively large installation space.